Bone marrow donation is not an easy thing. However, it is a heroic thing. You are very personally and quite literally, saving someone's life that you will likely never meet (what a world we live in!). With blood donation, it's a bit less connected, at least here in the US. They tell you that you are saving up to 3 people's lives. But outside of the donation station, you never really think about it again or hear from anyone about it. With marrow donation, you, and only you, are the reason that another real person is alive [1]. It's much more, well, intimate(?) than with blood donation.
Also, as HN tends to be a bit more on the paranoid side, I checked and they do NOT store any genetic information about you. Only the lymphocyte tests are stored via HIPAA compliance and are deleted when you decide to go off the registry. It seems that they are not very shady, so to speak, and really are trying to save lives and nothing else.
Please, if you are able, consider becoming a donor today.
Be an honest-to-God, real, actual Hero today.
[1] Not to discount all the staff, nurses, doctors, researchers, financial donors, etc.
For one reason or another they don't link directly to those organisations, but if you have the name, you should be able to find out the rest.